As optical communication technique penetrates as a basic technique of the information communication system, optical waveguide becomes more and more important as an optical network key device, and its development is proceeding toward the application to optical electronic circuit wiring substrate and the like. For prevalence of optical waveguide devices, the price reduction and the mass production are desired. Resin-made optical waveguides, which are easy in handling, have been developed as their powerful candidates. As waveguide-use resin materials, there are used fluorinated polyimide resin, deuterated polysiloxane resin, epoxy resin, perfluorinated alicyclic resin, acrylic resin, silicone resin and the like.
For prevalence of optical waveguide devices, it is necessary to have an optical path changing technique that sharply bends an optical circuit in order have an efficient connection between devices, particularly a multichannel optical path changing device that can send and receive a plurality of optical signals in parallel, such as 2-16 channels. Furthermore, there is a demand for an optical path changing device that has little loss, even characteristics between channels, and low cost.
As an optical path changing member, there is proposed a multichannel optical path changing member produced by opposing inclined end surfaces of a pair of optical waveguides that have the inclined end surfaces at one ends and roughly identical inclination angles of the inclined end surfaces and the optical waveguide core sizes, arrangements and the like in the inclined end surfaces, by connecting the inclined end surfaces with each other in a manner that the cores of the waveguides in the inclined end surfaces roughly coincide with each other, by fixing the pair of optical waveguides to have a rough V-shape, by removing an apex portion of the V-shaped optical waveguide to expose the core to a predetermined position, by laminating in parallel ones provided with reflecting surfaces at predetermined intervals, and by covering that with a substance having a refractive index lower than that of the core (see Patent Publication 1).
However, it is necessary to have precision operations such as a step of producing waveguides having inclined surfaces that conform to each other, a step of attaching these, and the like. Therefore, the steps are complicated. It tends to have a positional displacement between a vertical waveguide and a horizontal waveguide by separately producing the horizontal waveguide and the vertical waveguide. Thus, loss is likely to increase.
Furthermore, there is proposed a method in which a waveguide is horizontally formed on a substrate, then a reflecting mirror is formed, then a cladding layer film is formed, then a vertical opening portion is formed on the horizontal waveguide, and then light is passed through a hollow portion (see Patent Publication 2).
In this case, there occur light reflection and scattering at a boundary between the core and the hollow portion, and thereby loss increases. Even in case that the hollow portion is filled with a core material, there is likely to occur a positional displacement between the vertical waveguide and the horizontal waveguide, since the horizontal waveguide and the vertical waveguide are separately produced. Furthermore, an interface is generated at a core boundary between the horizontal portion and the vertical portion. This becomes a cause of the loss increase.
Patent Publication 1: Japanese Patent Laid-open Publication 2001-194540
Patent Publication 2: Japanese Patent Laid-open Publication 2000-193838